I love spotting wildlife in the forest garden. I noticed this beetle at the top of a bamboo cane earlier this month. The cane was next to a patch of rhubarb and a large partly rotten oak log that I use as a bench. I think it might be a lesser stag bettle (Dorcus parallelipipedus), which according to this website live in rotten wood of deciduous trees as larvae and then emerge to mate. I guess it is pole climbing looking for a partner or getting ready to fly off.